带电多孔介质中的超限离子传输与反应限制
Overlimiting Ion Transport and Reaction Limitations in Charged Porous Media
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- Massachusetts Institute of Technology（麻省理工学院）
- Department of Chemical Engineering, Massachusetts Institute of Technology（麻省理工学院化学工程系）
- Department of Mathematics, Massachusetts Institute of Technology（麻省理工学院数学系）
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中文总结 AI 辅助
本研究结合一维渗漏膜模型与CIET动力学，探究带电多孔介质中超限离子传输与反应限制的相互作用，推导了不同电荷多孔介质的极限电流表达式，为区分电化学系统的限制响应提供框架。
中文摘要 AI 辅助
电化学反应速率受界面电荷转移动力学与反应离子传输共同控制。在带电多孔介质中，固定电荷会在孔壁附近富集反应性对离子，使离子通过表面传导（SC）实现超出经典扩散极限的传输。在超限条件下，经典Butler-Volmer动力学预测电流随过电势无限增大，这与微观电子转移理论形成对比，后者设定了有限的反应限制电流。本研究将一维渗漏膜模型与耦合离子-电子转移（CIET）动力学结合，探究传输与反应限制的相互作用。极限行为由无量纲表面电荷（$\tilde{\rho}_s$）和对比反应限制电流与扩散限制电流的Damköhler数（$Da$）控制。我们推导了中性、带正电及带负电多孔介质的解析极限电流表达式，在$(Da,\tilde{\rho}_s)$平面上绘制了欠限到超限的转变。通过防止反应性离子耗尽，SC恢复了极化曲线对电荷转移动力学的敏感性，否则该敏感性会被扩散限制掩盖。对已发表的带电AAO膜中Cu电沉积数据拟合得到$Da\neq24$；拟合至AAO(-)的CIET参数也能描述AAO(+)，并预测了超出施加电压范围的有限AAO(-)反应极限。这些结果为区分电化学系统中传输限制与反应限制响应提供了框架，并确立带电多孔介质作为揭示电化学反应动力学参数的平台。
英文摘要
Electrochemical reaction rates are controlled by both interfacial charge-transfer kinetics and reactive-ion transport. In charged porous media, fixed charges enrich reactive counterions near pore walls, enabling transport beyond the classical diffusion limit via surface conduction (SC). Under overlimiting conditions, classical Butler-Volmer kinetics predict indefinitely increasing current with overpotential, contrasting with microscopic electron-transfer theories, which impose a finite reaction-limited current. Here, we couple the one-dimensional leaky membrane model to coupled ion-electron transfer (CIET) kinetics to examine the interplay between transport and reaction limitations. The limiting behavior is governed by the scaled surface charge $(\tildeρ_s)$ and a Damköhler number $(Da)$ comparing reaction-limited and diffusion-limited currents. We derive analytical limiting-current expressions for neutral, positive, and negatively charged porous media, mapping underlimiting-to-overlimiting transitions in the $(Da,\tildeρ_s)$ plane. By preventing reactive-ion depletion, SC restores polarization-curve sensitivity to charge-transfer kinetics that would otherwise be obscured by diffusion limitation. Fitting to published Cu electrodeposition data in charged AAO membranes yields $Da\approx24$. CIET parameters fitted to AAO($-$) also describe AAO($+$) and predict a finite AAO($-$) reaction limit beyond the applied voltage range. These results provide a framework for distinguishing transport-limited and reaction-limited responses in electrochemical systems and establish charged porous media as platforms to reveal electrochemical reaction-kinetic descriptors.
